Many lipophilic anti-platelet agents such as clopidogrel are only sparingly or negligibly water-soluble. The poor water-solubility of these agents often results in major difficulties in formulation, particularly when intravenous solutions are needed. A number of approaches for preparing intravenous compositions of sparingly or poorly water-soluble drugs are available. These methods include: physio-chemical solubilization techniques such as micellar solubilization by means of surface-active agents, formation of complexes, solid solutions and solid dispersions by means of the use of suitable polymers; use of various co-solvent systems; and use of the formation of complexes by the addition of chelating agents such as citric acid, tartaric acid, amino acids, thioglycolic acid, and edetate sodium. Other approaches are the use of buffering agents such as acetate, citrate, glutamate and phosphate salts. However, buffers and chelating agents have been implicated in adverse effects such as nephrotoxicity and renal tubular necrosis. Each of these methods has its inherent limitations and the solubility levels that can be achieved with the methods discussed above are still insufficient to make their use in intravenous commercial products.
U.S. Pat. No. 7,148,211 describes parenteral formulation of several representative therapeutic agents including anti-platelet agents such as clopidogrel. It is described in U.S. '211 how a parenteral formulation can be prepared with the lipophilic drug clopidogrel, a non-ionic solubilizer polysorbate 20 present at a concentration of about 0.05% to about 5% with or without the lipophilic antioxidant butylated hydroxytoluene (BHT) present at a concentration of about 20 to about 2000 ppm. Additionally ethanol can be present at a concentration of 0 to 30% with or without an aqueous vehicle.
In another example, Acusphere has described their Imagify® technology that uses perfluorobutane polymer microspheres for dissolving water-insoluble drugs such as clopidogrel.
Sanofi-Aventis atents U.S. Pat. Nos. 5,576,328 and 5,989,578 describe the use of parenteral preparations of clopidogrel and a pharmaceutically acceptable acid addition salt together with a pharmaceutically acceptable carrier.
For parenteral, intranasal, or intramuscular administrations, aqueous suspensions and isotonic and injectable solutions are used that contain dispersing agents and/or wetting agents that are pharmacologically compatible (e.g., propylene glycol or butylene glycol). The active ingredient is provided in the form of a complex with cyclodextrin, (e.g., α, β, or gamma cyclodextrin or 2-hydroxypropyl-β-cyclodextrin).
US Patent Publication 2006/0171948 by Regeneron Pharmaceuticals describes administration by subcutaneous or IV injection or infusion of antiplatelet agents such as clopidogrel. This patent publication describes the use of microspheres for sterile filling and using a technology from CyDex Corporation that employes cyclodextrin and captisol for solubilization.
There still is a need for pharmaceutical formulations of lipophilic anti-platelet agents such as clopidogrel that overcome the limitations of the above described approaches.